This invention relates generally to systems and methods for controlling and monitoring the condition of a patient. More specifically, this invention relates to an infusion fluid delivery system including the capability for obtaining periodic bedside measurements of patient blood chemistry.
Fluid infusion delivery systems in general are well known for infusing a selected fluid into a patient at a controlled flow rate and/or pressure. Such infusion delivery systems are used primarily with hospitalized patients to administer a variety of fluids including, for example, saline solutions, nutrients, drugs, and the like. Fluid infusion is normally accomplished by gravity flow and/or in conjunction with automated controllers or pumps through a flexible infusion line and further through a catheter inserted intravenously into the patient.
In recent years, patient blood chemistry and monitoring thereof has been recognized as an important information tool for improved patient care. For example, measurement of blood electrolytes, such as potassium, sodium, calcium, and chloride, can provide the physician with important information regarding patient condition and requisite treatment regimens. In the past, such measurements have been obtained by drawing a patient blood sample and then transporting the sample to an appropriate laboratory facility for analysis. However, blood chemistry levels can change rapidly and dramatically within a short period of time whereby the laboratory test data can be outdated before it can be returned to the attending physician. Moreover, repeated drawing and analysis of patient blood samples with a requisite frequency of perhaps several times each day substantially increases the cost of patient care and further results in significant inconvenience or discomfort to the patient.
Some attempts have been made to design a blood chemistry sensor for intravenous installation to provide continuous or rapid frequency in vivo blood chemistry measurements. See, for example, U.S. Pat. No. 4,340,457 which discloses miniature ion selective electrodes mounted on a catheter or needle structure for direct placement into a patient's bloodstream. However, significant manufacturing problems particularly with respect to sensor miniaturization have been encountered in electrochemical sensors for in vivo use. Moreover, proposed in vivo sensors are subject to contamination from prolonged exposure to patient blood thereby limiting sensor life and accuracy when inserted into the patient's bloodstream.
There exists, therefore, a significant need for a practical and economic blood chemistry monitoring system for obtaining frequent blood chemistry measurements at patient bedside without requiring substantial miniaturization of electrochemical sensors and further without requiring frequent insertion of needles or catheters into the patient. The present invention fulfills these needs and provides further related advantages by providing a combined blood chemistry monitoring and infusion fluid delivery system.